Metro Council considers financial incentive for green roofs

Metro officials have mapped out a system to offer financial incentives to businesses and homeowners that build green roofs under an ordinance the Metro Council will consider Tuesday.

The bill, which Metro Water Services helped draft, would deliver a reduction of sewer charges for up to five years to customers in large swaths of Davidson County’s urban core that have green roofs covering at least 50 percent of their rooftops. The reduction would apply to new and existing green roofs.

Sonia Harvat, spokeswoman for the water department, told The City Paper the measure is aimed at encouraging the construction of green roofs.

“Not only will this reduce overflows to the Cumberland River, but green roofs improve air quality, reduce heating and cooling costs, mitigate the city’s heat island effect and provide green space to urban areas,” she said.

The legislation, set for a second of three council votes on Tuesday, offers a credit of $10 for each square foot of the green roof. The measure would apply only to customers who live in the older parts of Nashville that are part of the city’s combined sewer system. This includes much of downtown and surrounding neighborhoods, East Nashville, and the area along West End Avenue near Vanderbilt University.

The measure would not offer financial aid for the 178,000-square-foot green roof set to go atop Nashville’s Music City Center, which does not feed into the city’s combined sewer system. In addition, bill sponsors –– council members Sean McGuire and Walter Hunt –– have proposed an amendment that would exclude all publicly owned buildings from the incentive.

Monthly charges for water and sewage are based on metered water consumption. Rates vary between commercial and residential [1] property owners.

The green-roof credit would be awarded each month to ratepayers until their full credit expires or 60 months have lapsed –– whichever comes first. The water department has set a cap of $500,000 annually for distribution collectively among all properties that qualify for the program. The reduction would be delivered on a first-come-first-served basis.

Revenues collected from water and sewer fees goes toward the water department’s operating budget.

Mayor Karl Dean’s Green Ribbon Committee on Environmental Sustainability encouraged ways to spur more green roofs in a 2009 report.

Customers would need to submit documentation annually to receive the credit. Eligible green roofs, in addition to covering half a rooftop, would need the following components:

• a waterproof membrane layer;

• a drainage layer designed such that roof drains can be inspected and cleaned;

• a growth medium at least four inches in depth; and

• a vegetation layer, at least 80 percent of which must consist of live, hardy, drought-resistant plants.